An HDD (Hard Disk Drive), for example, is installed as a storage device in the disk array apparatus. The HDD is configured of, for example, a drive mechanism which rotates and drives a plurality of magnetic disks, an arm rotatably supported on a pivot, a magnetic head fixed to the arm, an actuator which performs positioning control of the magnetic head to a target position on the magnetic disk, for example, a target track or a target cylinder, and others.
Recently, pursuant to the increase in the recording density of magnetic disks, the recording track width and the sector width on the magnetic disks are becoming narrower, and high accuracy is demanded for positioning magnetic heads. Consequently, an allowable range of gap in magnetic head positioning is becoming narrower.
As one of the causes interfering the improvement of the accuracy of magnetic head positioning, positioning errors which occur when the magnetic heads are vibrated can be named.
Since a magnetic head is fixed to the arm and the arm is rotatably supported on the pivot, if rotation vibration centering on a rotation axis normal to the magnetic disk surface occurs in the HDD, this rotation vibration will affect magnetic head positioning. Consequently, for maximizing the HDD performance, it becomes extremely important to reduce the rotation vibration whose rotation center is the rotation axis normal to the magnetic disk surface.
As a method for reducing the influence of the vibration, for example, a method in which a rapid change of acceleration due to the vibration is inhibited by incorporating a spring between the HDD unit and a substrate housing the HDD unit is proposed (refer to Patent Literature 1).
Furthermore, a method in which vibration energy is reduced by incorporating a dynamic absorber in a main chassis supporting a motor which drives optical disks is proposed (refer to Patent Literature 2 and Patent Literature 3). Furthermore, a magnetic disk apparatus in which head positioning errors are reduced even if rotation vibration in the planar direction parallel to the recording surface of the disk occurs is proposed (refer to Patent Literature 4).
Furthermore, a magnetic disk apparatus which sets a set of vibration detectors which detect rotation vibration contents in one axial direction as vibration detectors used for disturbance compensation of rotation vibration acting on the rotary actuator, before performing digital conversion for the detected data of rotation vibration, ascertains a difference of vibration detection signals by the set of vibration detectors in an analog computing circuit, inputs the difference in an AD converter, and processes the data in one AD converter is proposed (refer to Patent Literature 5).
Citation List
Patent Literature
    PTL 1: Japanese Patent Application Laid-Open (Kokai) No. 2002-319280    PTL 2: Japanese Patent Application Laid-Open (Kokai) No. 2004-134045    PTL 3: Japanese Patent Application Laid-Open (Kokai) No. 2006-185496    PTL 4: Japanese Patent Application Laid-Open (Kokai) No. 2001-291363    PTL 5: International Publication No. 2008/139586